1. Field of Invention
The present invention relates to window blind, more particularly, relates to a lift cord operation system for improving and smoothing out the operation of the window blind so as to provide a diversified shading effect.
2. Description of Related Arts
Blinds and the like such as drapes and portieres are commonly used for sheltering window, separating spaces, and etc., since they are easily maneuverable and aesthetically appealing. Most of the blind comprise a head rail, a bottom rail, a plurality of hanging nets downwardly extended from the head rail to the bottom rail for horizontally and suspendedly supporting a plurality of slats, wherein the slats could be shifted in a vertical movable manner by a lifting mechanism, and individually rotated at the same time.
Here, the lift mechanism is adapted to lift the bottom rail to a desired elevation for selectively allowing the window to be exposed to an exterior thereof. Commonly, the lifting mechanism comprises a plurality of operation cords operated by the user to adjust the elevation or shading status of the window blinds.
Typically, the head rail is a U-shaped elongated channel having a shaft longitudinally provided thereon in for supporting the hanging nets, and at least an opening is cut in the bottom of the U-shaped channel through which the pull cords exited for operating the slats movement.
However, the traditional window blind has several drawbacks. When the slats are upwardly received, sunlight would directly enter the window thus not only heating up the interior of a house but also unpleasing to people's eye. Furthermore, there is no privacy at all because the interior of the house is easily viewed from outside. On the other hand, when the bottom rail is downwardly lowered, sunlight would be shining through from slat gaps. Here, the size of the slat gap is set by the manufacturer so that the user could not make a change. Therefore, user unwillingly has to make a tough decision between privacy and light from predetermined gap. Or helplessly, user might alternatively turn on the light lamp in order to brighten up the interior space.
Based on this situation, an amended window blind, which is capable of providing varying shading effects, have emerged into existence nowadays. This multifunctional window blind comprises an alternation hanging device extended from the head rail for sustaining a predetermined set of the slats, preferably half of the slats, and an alternation-operating lift cord are provided for lifting up the alternation hanging device so as to upwardly move the predetermined set of slats overlapping with remaining slats for doubling the size of the slat gap.
In other words, this kind of window blind system provides two sets of hanging device for simultaneously supporting a set of slats, wherein the ladder-shaped hanging net of the alternation hanging device supports only a predetermined portion of the slats so as to provide a varying shading effect. Every other slat not supported by the alternation hanging device must be adjacent to slats supported by the alternation hanging device.
Accordingly, all top ends of respective elongated hanging nets of the alternation hanging device are merged into a lift cord. Theoretically, by pulling the lift cord, the alternation hanging device could be lifted up to enlarge the slat gap.
For convenient operation, the lift cord is escaped from the head rail and dangling outside to be gripped by the user. The lift cord is adapted to be disposed at one side of the window so as not to block the light shining through the window. Generally, the user could choose a preference as to whether the lift cords and operation cords be disposed on the right side or the left side of the window.
Unfortunately, this lift cord disposed on the side end of the window would impose a cumbersome problem for the user.
For a wider window blind, there are pluralities of ladder-shaped hanging nets spacedly disposed for evenly lifting up the alternation hanging device. However, once the dangling lift cord is pulled, the hanging net positioned at close end to the lift cord would withstand a relatively stronger tension force. Instead, the hanging net disposed at far end with respect to the pulled lift cord would bear a relatively weaker tension force. It is highly unlikely for a user to balancedly lift up the whole alternation hanging device. Most of the time, the alternation hanging device would be lifted up with a tilted angle.
Furthermore, there are several bottom openings spacedly defined at the head rail for exiting the respective hanging net of such alternation hanging device. The lift cords under such a tension would cause a portion of the hanging net repeatedly and reciprocally rub with the head rail body. Even a pulley device could be provided at such openings, there is no guarantee that the hanging net would be passing in and out from the head rail in a smooth manner. In a long run, such an unbalanced tension would cause the lift rod close to the adjacent hanging net worn off or broken.
Moreover, both of the aforementioned lift cord and operation cord utilize cord lifting lock, which is mounted within the head rail, for retaining the lift cord and operation cord in position. Conventionally, the operation cords extend from a bottom rail through the slats and into the head rail. The cords could be collected within the head rail, or more typically, exit one end of the head rail to be dangling outside.
Commonly, the lift lock comprises a lock housing integrally defined within the head rail, a stationary roller journalled in the housing, and a floating gear wheel disposed moveably in the housing from an unlocked position to a locked position, wherein the lift cord is sliding between the stationary roller and the floating gear wheel for moving the floating gear wheel from the unlocked position to the locked position, in the unlocked position, the lift cord could be slide over the floating gear wheel to permit lifting and lowering of the slats, and in the locked position, the floating gear wheel is clamped between the stationary roller and the housing so that the lift cord is stuck between the floating gear wheel and the stationary roller.
Unfortunately, once the lift lock is utilized to lock the lifted alternation hanging device, the lift lock would withstand overall weight of the alternation hanging device, the floating gear wheel would be released a little bit for biasing against the lift cord. For conventional operation cords, the homing movement of the floating gear wheel could ensure the operation rod securely stuck between the stationary roller and the floating gear wheel. However, for the alternation hanging device, which is adapted to lift up half of the slats tightly overlapped with remaining half of the slats for enlarging the slat gap. This homing release would be undesirable even intolerable to most users. This is due to the fact that the homing movement of the floating gear wheel would lower the predetermined set of the slats supported by the alternation hanging device away from the remaining slats thus ruining the shading effect.